In general, a compressor serving to compress a refrigerant in a vehicle cooling system has been developed in various forms. The compressor includes a reciprocating compressor that compresses a refrigerant during reciprocation and a rotary compressor that compresses a refrigerant during rotation.
The reciprocating compressor includes a crank compressor that transmits driving force from a drive source to a plurality of pistons using a crank, a swash plate compressor that transmits driving force from a drive source to a rotary shaft equipped with a swash plate, and a wobble plate compressor that uses a wobble plate. The rotary compressor includes a vane rotary compressor that uses a rotary shaft and a vane, and a scroll compressor that uses an orbiting scroll and a fixed scroll.
In the compressor, a sliding part is lubricated with oil, and the oil is separated and recovered from a compressed refrigerant and is then resupplied to the sliding part since the oil is mixed with the refrigerant.
That is, a conventional compressor includes a compression mechanism that sucks a refrigerant from a suction space by diving force transmitted thereto and compresses the refrigerant to discharge it to a discharge space, an oil storage chamber that is provided in the discharge space to collect oil separated from the refrigerant discharged from the compression mechanism, and an oil recovery passage that guides the oil in the oil storage chamber to the suction space.
Here, the oil storage chamber is a high-pressure region and the suction space is a low-pressure region. Therefore, it is possible to prevent a deterioration in compressor performance and a power loss only if oil is sufficiently decompressed when the oil is introduced into the suction space through the oil recovery passage.
Accordingly, in the conventional compressor, the oil recovery passage is provided with a decompression mechanism that reduces the pressure of the oil passing through the oil recovery passage by an orifice hole having an inner diameter smaller than the oil recovery passage.
FIG. 1 is a perspective view illustrating a decompression mechanism in a conventional compressor. FIG. 2 is a cross-sectional view illustrating a state in which the decompression mechanism of FIG. 1 is mounted to the compressor.
Referring to FIGS. 1 and 2, a conventional decompression mechanism 58 includes an orifice member 582 formed with an orifice hole 582d. 
The orifice member 582 has a tubular shape and include the orifice hole 582d formed at the center side thereof to pass through the orifice member 582.
The orifice member 582 is made of a rigid material such as copper with a predetermined rigidity such that the length and inner diameter of the orifice hole 582d are a predetermined value. Here, the length and inner diameter of the orifice hole 582d are factors that determine a decompression capacity of the orifice member 582. The decompression capacity of the orifice member 582 is increased as the length of the orifice hole 582d is long and the inner diameter of the orifice hole 582d is short.
However, in the conventional compressor including the decompression mechanism 58, if the pressure in an oil storage chamber 54 is increased, the oil recovered from the oil storage chamber 54 to a suction space S1 is not sufficiently decompressed, which may lead to a deterioration in compressor performance and a power loss. In more detail, the pressure of the refrigerant discharged from a compression mechanism (not shown) is irregular, and may be higher than a predetermined pressure value. Thus, the pressure in the oil storage chamber 54 may be higher than a predetermined pressure value. However, since the length and inner diameter of the orifice hole 582d are fixed to be a predetermined value, the decompression capacity of the decompression mechanism 58 (more exactly, the orifice member 582) is fixed. Accordingly, when the pressure in the oil storage chamber 54 is higher than a predetermined pressure value, the pressure of the oil passing through the decompression mechanism 58 is higher than a predetermined pressure value. That is, as the pressure in the oil storage chamber 54 is increased, the flow rate of oil passing through the decompression mechanism 58 is increased, with the consequence that the oil, which is not sufficiently decompressed, is introduced into the suction space S1. Hence, the pressure in the suction space S1 is higher than a predetermined pressure value, resulting in a deterioration in compressor performance and a power loss.